Lightout protection for 3-block 4-indication signalling system



Feb. 28, 1956 DODD 2,736,794

LIGHTOUT PROTECTION FOR 5-BLOCK 4-INDICATION SIGNALLING SYSTEM FiledOct. 25, 1951 2 Sheets-Sheet 1 HIS A T TOHIVE' Y 4 um m n R m ELI-H m n.Q J m w 3% kiu E RES u m, fi m m. h m I f 1| EN M F Em Hum r mam m\. 1FN m Feb. 28, 1956 A. E. DODD LIGHTOUT PROTECTION FOR 3-BLOCK4-INDICATION SIGNALLING SYSTEM 2 Sheets-Sheet 2 E @M RE m ETk L m Q m mww vfi m m fiTm sfi m SR NQR Wu k fi R min W R INVENTOR.

Arthur E Dodd Filed 001;. 25, 1951 United States Patent 9 LHGHTOUTPROTECTION FOR 3-BLOCK l-lNDlCATION SIGNALLING SYSTEM Arthur E. Dodd,Edgewood, Pa., assignor to Westinghouse Air Brake Company, Wilmerding,Pa., a corporation of Pennsylvania Application October 25, 1951, SerialNo. 253,156

Claims. (Cl. 246-50) My invention relates to a railway signal controlsystem. More particularly, my invention relates to a lightont protectionscheme for a railway signaling system which embodies light signals ofsuch, for example, as the well-known Searchlight type.

Lightout protection schemes have previously been devised for steadylight aspects in two-block indication signaling systems embodyingsignals of the color light type or of the Searchlight type.

An object of my invention is the provision of a lightout protectionarrangement for a railway signaling system in which the signals arenormally not lighted but are controlled to become lighted in response tothe approach of a train, and in which each signal at times displays aflashing light aspect.

A feature of my invention for accomplishing this object is anarrangement in which a lightout relay has a high resistance winding anda low resistance winding energized by pickup circuits including frontand back contacts respectively of an approach relay and energizedalternately by stick circuits while a flashing light signal aspect isbeing displayed.

I shall describe two forms of apparatus embodying my invention, andshall then point out the novel features thereof in claims.

in the accompanying drawings, Figs. la and lb, when placed end to end,with Fig. In on the left, constitute a diagrammatic view showing oneform of apparatus embodying my invention, in which a lightout relayhaving a high resistance winding and a low resistance winding isprovided for each signal in a three-block four-indication signalingsystem; in which each signal is of. the Searchlight type; in which eachsignal is normally not lighted, but is controlled to become lighted inresponse to an approaching train; and in which each signal at timesdisplays a flashing light aspect.

Fig. 2 is a diagrammatic view showing a modified form of the apparatusassociated with each signal in Fig. 1, also embodying my invention, inwhich provision is made for normally lighting each signal'by alternatingcurrent energy, and for lighting each signal by direct current energy inthe event of failure of the alternating current source.

Similar reference characters refer to similar parts in each of theviews.

Referring further to Figs. la and lb of the drawings, a stretch ofrailway track is shown, over which trafiic movements are normally madein the direction indicated by the arrow. In order to simplify thedrawings, each track, comprising two parallel series of track rails, isrepresented by a single line.

The stretch of track is divided by insulated joints 5 into sectionsdesignated by the reference characters 0T, 1T, 2T, and ST. A portion ofa section, designated by the reference character 4T, is also shown atthe righthand end of Fig. 1b. Each of the sections 0T, 1T, 2T and ST isprovided with a track circuit including a suitable source of currentsuch, for example, as a battery 6,

connected across the rails adjacent one end of the section, and a trackrelay, designated by the reference char acter R preceded by thereference character for the corresponding section, connected across therails adjacent the opposite end of the section.

Signals, designated by the reference characters 18, 28, 3S and 45, arelocated adjacent the entrance end of sections 1T, 2T, ST and 4T,respectively, for governing trafiic movements toward the right, as shownin the drawings, which I shall assume is the eastbound direction. Thelength of track between each signal and the next signal in advance isknown as a block, and therefore each of the sections 0T, 1T, 2T and STconstitutes a block.

Each of the signals, as shown in the drawings, is of the well-knownSearchlight type such, for example, as shown in Letters Patent of theUnited States No. 1,864,224, granted June 21, 1932, to Wesley B. Wells,for Light Signals. Each of the signals has a mechanism, designated bythe reference character G preceded by the numeral in the referencecharacter for the corresponding signal, and has a lamp, designated bythe reference character E preceded by the numeral in the referencecharacter for the corresponding signal. The mechanism G of each signaloperates a spectacle in which there are three filters which may be ofthe colors,- green, yellow and red, respectively. When the mechanism Gfor a signal is energized by current of normal polarity, the mechanism Gmoves the green filter in front of the lamp E, so that the signaldisplays a green aspect; when the mechanism G is energized by current ofreverse polarity, it moves the yellow filter in front of the lamp E, sothat the signal then displays a yellow aspect; and when the mechanism Gis deenergized, it moves the red filter in front of the lamp E, so thatthe signal then displays a red aspect. I

In the arrangement shown in the accompanying drawings, each of thesignals is controlled to display three different proceed indications, aswell as a stop indication, in a three-block, four-indication signalingsystem, as shown by the following tabulation:

The mechanism G of each signal is controlled by a home control relay,designated by the reference character HR preceded by the numeral in thereference character for the corresponding signal, and by a distantcontrol relay, designated by the reference character HDR preceded by thenumeral in the reference character for the corresponding signal. Eachrelay HDR is of .the retained neutral type, that is, its front contactsare slow releasing and remain closed during a reversal of polarity ofthe current supplied to the control winding of the relay.

An approach control relay for the lamp for each signal is designated bythe reference character AR preceded by the numeral in the referencecharacter for the corresponding signal. Each approach control relay ARis controlled by a front contact of the track relay for the first blockin the rear of the corresponding signal and by a front contact of thetrack relay for the first block in advance of the corresponding signal.

The home control relay HR for each signal iscontrolled by a frontcontact of the track relay for the first 3 block in advance of thecorresponding signal, and by a front contact of a lightout relay,designated by the reference character LOR preceded by the numeral in thereference character for the corresponding signal.

Each lightout relay LOR has two control windings, one of which I shallcall the first winding, designated by the reference character 1000,having a high resistance which may be of the order of 1000 ohms, and theother winding which I shall call the second winding, designated by thereference character 0.58, having a low resistance which may be of theorder of 0.58 ohms.

Each distant control relay HDR is controlled by a front contact of thehome control relay HR for the corresponding signal, and by a frontcontact of the relay HR for the first signal in advance of thecorresponding signal, and also by pole-changing contacts of the HR relayfor the second signal in advance of the corresponding signal.

A flashing yellow control relay for each signal designated by thereference character FYR preceded by the numeral in the referencecharacter for the corresponding signal. Each relay FYR is controlled bya front contact and by a reverse polar contact of the HDR relay for thecorresponding signal.

A flasher relay for each signal is designated by the reference characterFR preceded by the numeral in the reference character for thecorresponding signal. Each relay PR is of a type which, while it isenergized, will repeatedly close and open its front and back contactsalternately at a frequency which may be of the order of 40 times perminute.

Each relay LOR has pickup circuits for its high and low resistancewindings controlled over front and back points, respectively, ofcontacts of the AR relay for the corresponding signal, and has stickcircuits for these windings which are repeatedly closed alternately 40times per minute by front and back contacts, respectively, of the FRrelay for the corresponding signal. Each relay LOR is made slowreleasing by an asymmetric unit, designated by the reference character1', which may be of the well-known halfwave copper oxide rectifier type,connected across the low resistance winding of the LOR relay in adirection to oppose the flow of current in multiple with the lowresistance winding of the LOR relay.

The lighting of lamp E for each signal is controlled by the relays AR,FYR, PR and LOR for the corresponding signal. Each lamp E is at timesconnected in series with the high resistance winding of the LOR relayfor the corresponding signal, and is at other times connected in serieswith the low resistance winding of the LOR relay for the correspondingsignal. The relation between the resistances of the windings of the LORrelays and the lamps E is such that, when a lamp E is connected inseries with a high resistance winding, the lamp will not be lighted butwill remain dark, and when a lamp E is connected in series with a lowresistance winding, the lamp will be lighted.

An energy storing device for each signal, shown as a capacitordesignated by the reference character c, is controlled to become chargedby a circuit which includes a front contact of the LOR relay for thecorresponding signal and a back contact of the flasher relay for thecorresponding signal. When the flasher relay closes its front contact,the capacitor will then discharge through the high resistance winding ofthe corresponding LOR relay for retaining the LOR relay in the picked-upcondition.

The control circuits and lamps may be supplied with energizing currentby any suitable source such, for example, as a battery shown in Fig. la,designated by the reference character Q and having terminals B and N.

In the modified form of apparatus shown in Fig. 2, all parts of theapparatus shown in Figs. la and lb are controlled as in Figs. 1a and lbexcept that the energizing circuits for the lamps E in series witlrthelow resistance windings 0.58 of relays LOR are modified so that normallythey are supplied with alternating current, and are supplied with directcurrent when the source of alternating current fails. The source ofalternating current may be a generator, designated by the referencecharacter ACG, as shown in Fig. 2 having terminals BX and NX.

A power-01f relay, designated by the reference character POR, isconnected directly across terminals BX and NX, and is therefore normallyenergized, but becomes deenergized when the alternating current sourcefails. Alternating current is normally supplied from generator ACGthrough front points of contacts of relay POR, and direct current issupplied from a battery Q through the back points of these contacts,when the alternating current source fails.

Having described, in general, the arrangement and control of the variousparts of apparatus embodying my invention, I shall now describe thecircuits and operation in detail.

As shown in the drawings, all parts of the apparatus are in the normalcondition, that is, the stretch of track is unoccupied, and thereforethe track relays are all energized; the mechanism G of each of thesignals is energized by current of normal polarity, and therefore eachmecha nism G is in the clear proceed position, with the green filter infront of the lamp E which is, however, not lighted; relays lHDR, ZHDRand 3HDR are energized by current of normal polarity; relays IAR, 2AR,3AR, lI-IR, ZHR and SHR are energized; the high resistance winding ofeach of the relays ILOR, ZLOR and 3LOR is energized in series with thelamp E for the corresponding signal, and therefore the lamps E are notlighted; relays lFYR, ZFYR, 3FYR, IFR, ZFR and SFR, and the lowresistance winding of each of the relays lLOR, 2LOR and 3LOR are alldeenergized; and the power-off relay POR, shown in Fig. 2, is energized.

Relay lAR is energized by a circuit passing from terminal B, throughcontacts 7 and 8 of relays OTR and 1TR, respectively, and the winding ofrelay llAR to terminal N. Each of the relays ZAR and 3AR is energized bya similar circuit which includes front contacts of the track relays forthe first block in the rear and the first block in advance of thecorresponding signal.

Relay lHR is energized by a circuit passing from terminal B, throughcontacts 13 and 14 of relays ITR and iLOR, respectively, and the windingof relay IHR to terminal N. Each of the relays ZHR and 3I-IR isenergized by a circuit which is similar to the circuit just traced forrelay IHR, which includes a front contact of the track relay for thefirst block in advance of the corresponding signal and a front contactof the lightout relay for the corresponding signal.

The circuit by which relay IHDR is energized by current of normalpolarity passes from terminal B, through the front point of contact 19of relay SHR, front contacts 20 and 21 of relays ZHR and lI-IR,respectively, the winding of relay IHDR, and the front point of contact22 of relay 3HR to terminal N. Each of the relays ZHDR and SHDR isenergized by current of normal polarity in a circuit which is similar tothe circuit just traced for relay lHDR, but only a portion of which isshown in the drawings.

Mechanism 1G is energized by current of normal polarity passing fromterminal B, through contact 25 of relay lHR, front neutral contact 26 ofrelay IHDR, normal polar contact 27 of relay IHDR, mechanism 1G, andcontacts 28 and 29 of relay IHDR to terminal N. Each of the mechanisms26 and 3G is energized by a circuit \iVhiCh is similar to the circuitjust traced for mechanism The high resistance winding of relay ILOR isenergized by a circuit passing from terminal B, through the highresistance winding of relay lLOR, front point of contact 43 of relayiAR, and lamp IE to terminal N. Lamp 1E, however, on account of beingconnected in serieswith. the high resistance winding of relay ILOR,

remains uulighted. The high resistance windings of relays Z LOR and3LOR, and lamps 2E and 3B, are energized by circuits which are similarto the circuit just traced for the high resistance winding of relay ILORand lamp 1E, and therefore each of the lamps 2E and SE is alsounlighted.

In the arrangement shown in Fig. 2, the high resistance winding of relaylLOR is energized by a circuit passing from terminal 13, through thehigh resistance winding of relay ILOR, front point of contact 63 ofrelay 1AR lamp 1E, and the front point of contact 69 of relay lAR toterminal N. Relay POR, shown in Fig. 2, is constantly connected acrossterminals BX and NX, and is therefore energized at all times except whenthe source of alternating current fails.

I shall assume that, with apparatus arranged as shown in Figs. 1a and lbof the accompanying drawings, an eastbound train enters section 0T,deenergizing relay 0TR. Contact 7 of relay 0TR will then open thecircuit traced for relay lAR, causing relay IAR to be deenergized.

With relay IAR deenergized, the energizing circuit for the highresistance winding of relay lLOR will be opened at the front point ofcontact 43 of relay IAR, and the pickup circuit for the low resistancewinding of relay 1LOR will be completed at the back point of contact 43of relay lAR, this circuit passing from terminal B, through the backpoint of contact 42 of relay IFYR, the low resistance winding of relayl-LOR in multiple with asymmetric unit 1', back point of contact 43 ofrelay 1AR, and lamp IE to terminal N. Lamp 1E, upon being connected inseries with the low resistance winding of relay ILOR, will becomelighted. As previously described, mechanism 16 is energized by currentof normal polarity, so that the green filter is in front of lamp 1E, andtherefore signal 18 will now display the steady green light aspect.

When the train enters section 1T, deenergizing relay lTR, contact 9 ofrelay iTR will open the circuit for relay ZAR, causing relay 2AR to bedeenergized, so that lamp 213 of signal 28 will then become lighted, andsignal 28 will be controlled to display the steady green light aspectsimilarly to signal 18, as previously described, in response to thetrain entering section 0T.

Also, with relay lTR deenergized, contact 13 of relay lTR will open thecircuit for relay lHR, and contact 8 of relay lTR will open the circuitfor relay IAR at another point. With relay iHR deenergized, the circuitfor relay IHDR will be opened at contact 21 of relay IHR, and thecircuit for mechanism 16 will be opened at contact 25 of relay lHR, sothat relay IHDR and mechanism 16 will both be deenergized. Mechanism 1Gwill therefore move the associated spectacle to the position in whichthe red filter is in front of lamp 1E, and therefore, with lamp 113lighted, signal 18 will now display the steady red light aspect. As longas the train remains on section 1T, relays lHR and lAR will bedeenergized, and therefore signal 15 will continue to dis play thesteady red light aspect as long as the train occupies block 1T.

When the train enters section 2T, deenergizing relay ZTR, relay 3AR willbe deenergized by the opening of contact 11 of relay ZTR, so that lamp3E will be lighted and signal 38 will be controlled to display thesteady green light aspect similarly to signals 18 and 28, as previouslydescribed, in response to the train entering sections GT and IT,respectively.

With relay ZTR deenergized, signal 28 will display a steady red lightaspect, as previously described for signal 18 in response to the trainentering section IT, and will continue to do so as long as the trainoccupies block 2T.

When the train leaves section 1T, relay lAR will again become energizedby its circuit previously traced. With relay lAR again energized, lampIE will be connected in series with the high resistance winding of relayILOR in the circuit previously traced, and therefore lamp 1E will becomeextinguished. RelaylI-LR will again be energized by its circuitpreviously traced, but relay ,IHDR will now remain deenergized onaccount of its circuit being open atcontact 20 of relay 2HR. With relayIHR energized and with relay IHDR deenergized, mechanism 16 will now beenergized by current of reverse polarity passing from terminal B,through contact 25 of relay ,lH-R, back point of contact 26 of relaylHDR, mechanism 16, and the back point of contact 29 of relay .lHDR toterminal N. With mechanism 1G energized by current of reverse polarity,mechanism 1G will move its spectacle to the position in which the yellowfilter will be in front of lamp IE, but since lamp IE is nowextinguished, signal 18 will remain dark.

When the train enters section 3T, deenergizing relay 3TR, contact 17 ofrelay 3TR will open the circuit for relay 3l-IR, causing relay SHR toalso be deenergized. Signal 38 will therefore display the steady redlight aspect, as previously described for signals 18 and 28. I

When the train leaves section 2T, relay 2AR will again become energizedby its circuit previously traced, and lamp 21E will be connected inseries with the high resistance winding of relay 2LOR, as previouslydescribed, so that lamp 213 will be extinguished. Relay ZHR will nowagain be energized by its circuit previously traced, but relay ZHDR willbe deenergized on account of contact 23 of relay 3HR being open.Mechanism 26 will therefore be energized by current of reverse polarity,as previously described, for signal 18.

With relays IHR and 2HR again energized and relay 3HR deenergized, relayIHDR will now be energized by current of reverse polarity in a circuitwhich is the same as the circuit previously described for this relayexcept that it includes the back points of contacts 19 and 22 of relaySHR instead of the front points of these contacts. With relay iI-IRenergized and with relay IHDR energized by current of reverse polarity,mechanism 16 will now be energized by current of reverse polarity inanother circuit passing from terminal B, through contact 25 of relaylHR, front point of contact 26 of relay IHDR, contact 27 of relay lHDRclosed in the reverse position, mechanism 16, contact 28 of relay lHDRclosed in the reverse position, and the front point of contact 29 ofrelay lHDR to terminal N. Mechanism 1G will therefore remain in thereverse position.

With relay IHDR energized by current of reverse polarity, relay IFYRwill now be energized by a circuit passing from terminal B, throughcontacts 55 and 56 of relay lHDR, and the winding of relay IFYR toterminal N. With relay IFYR energized, relay lFR will be energized by acircuit passing from terminal B, through the front point of contact 42of relay lFYR, and the winding of relay IFR to terminal N. The highresistance Winding of relay lLOR will now remain energized by its pickupcircuit previously traced through the front point of contact 43 of relay1AR, and lamp 1E, as previously described.

During the periods when contact 52 of relay lFR is closed at its backpoint, capacitor 0 will be charged by its circuit passing from terminalB, through the front point of contact 40 of relay ILOR, a resistor r,capacitor 0, and the back point of contact 52 of relay IFR to terminalN. During the periods when contact 52 of relay lFR is closed at itsfront point, capacitor c will be discharged through the high resistancewinding of relay lLOR by a circuit passing from capacitor c, throughresistor r, front point of contact 40 of relay ILOR, high resistancewinding of relay ILOR, and. the front point of contact 52 of relay iFR,back to capacitor c. Since the high resistance winding of relay ILOR isalready energized by its circuit through the front point of contact 43of relay EAR, the discharge of capacitor 0 will perform no usefulfunction at this time.

I shall now assume that, while the first train is on section 3T, asecond eastbound train enters section 0T, deenergizing relay IAR, aspreviously described, thereby opening the pickup circuit for the highresistance winding of; relay 1LOR through the front point ofcontact 43of relay IAR. The high resistance winding of relay lLOR will now beenergized, from capacitor by the stick circuit previously traced, whilecontact 52 of relay lFR is closed at its front point, and the lowresistance winding of relay lLOR will be energized when the contacts ofrelay lFR are closed at their back points. The circuit for energizingthe low resistance Winding Will pass from terminal B, through the frontpoint of contact 40 of relay ILOR, contact 41 of relay lFR, lowresistance winding of relay ILOR in multiple with asymmetric unit 2',back point of contact 43 of relay lAR, and lamp 1E to terminal N.

The high resistance winding of relay 1LOR is therefore energized by astick circuit while contact 52 of relay lFR is closed at its frontpoint, and the low resistance winding of relay lLOR is energized by astick circuit when contact 41 of relay IlFR becomes closed, so thatrelay lLOR retains its front contact 40 closed at the front point.During the periods while contact 41 of relay lFR is closed, lamp 113 isenergized in series with the low resistance winding of relay )lLOR, andtherefore lamp IE is A periodically lighted. Since mechanism 16 is nowin its reverse position, signal 18 will display its flashing yellowlight aspect.

When the first train leaves section 3T, relay 3AR will again becomeenergized by its circuit previously described, so that lamp 3E willagain be connected in series with the high resistance winding of relaySLOR, causing lamp SE to be extinguished. Relay SHR will now beenergized, and relay 3HDR will be deenergized while the train occupiesthe block 4T east of signal 45, so that mechanism 3G will be operated toits reverse position by a circuit which is similar to the first reversecontrol circuit previously traced for mechanism 16.

With relay SHR again energized, relay IHDR will be energized by currentof normal polarity in the circuit first traced for this relay. Mechanism1G will therefore be operated to its clear position, and relay IFYR willbecome deenergized, causing relay lPR to also be deenergized. With relayIiAR deenergized on account of the second train on. section il'i, lampIE will now again be lighted by its circuit previously traced throughthe back point of contact 42 of relay .lFYR and the back point ofcontact 43 of relay lAR, and signal will now again display the steadygreen light aspect.

With contacts 23 and 24 of relays 3HR and ZHR, respectively, now closed,relay ZHDR will be energized by current of reverse polarity in a circuitwhich is similar to the circuit previously traced for relay IHDR, aslong as the first train occupies the block 4T east of signal 43. Withrelay ZHR energized and relay ZHDR energized by current of reversepolarity, mechanism 2G will now be energized by current of reversepolarity in a circuit which is similar to the second circuit previouslytraced for energizing mechanism 16 by current of reverse polarity.

I shall next assume that again a first train occupies section 3T, andthat a second train has entered section 0T, causing signal 15 to displaythe flashing yellow light aspect, as previously described. I shallassume further that while the first train is still on block 3T, lamp 3Eburns out. With lamp 3E burned out, relay SLOR will be deenergized.Relay 3HR is, however, still deenergized on account of relay STR beingdeenergized, so that the burning out of lamp 3E will cause no change inthe indication displayed by signal 13.

When the first train now leaves block 3T, relay SLOR will remaindeenergized on account of lamp 3E being burned out, and therefore reiay3HR will remain deenergized, causing signal 13 to continue to displaythe flashing yellow light aspect instead of changing to the steady greenlight aspect, as previously described, when the first train left section3T with lamp 3E not burned out.

When the second train new enters section 1T, signal 18 will becontrolled to display the steady red light aspect as previouslydescribed when the first train entered section 1T. Now, however, signal28 will not display either the steady green light aspect or the flashingyellow light aspect since relay 2HDR is deenergized on account of relay3HR being deenergized, which is in turn deenergized on account of relay3LOR being deenergized. With relay ZHDR deenergized, mechanism 26 willnow be energized by current of reverse polarity, and relay ZFYR will bedeenergized, so that signal 25 will display the steady yellow lightaspect.

The operating rules of railroads usually require that a dark signal beobeyed as a stop signal. The arrangement shown in the accompanyingdrawings for displaying restrictive indications in the rear of a darksignal aids in removing the operating hazard of a sudden brakeapplication resulting from an unexpected dark signal.

The control and operation of the modified form of apparatus shown inFig. 2 is similar to that described for the apparatus associated withsignal 18 in Figs. la and lb. The circuits by which lamp 1E and the lowresistance winding of relay lLOR are normally energized by alternatingcurrent and by which they become energized by direct current when thesource of alternating current fails are believed to be obvious in viewof the description of the operation of the form of apparatus shown inFigs. la and 1b.

I have described the operation of the apparatus for a few typicaltraffiic situations. It is believed that, in view of the foregoingdescription, the operation of the apparatus for any other possibletrafiic situation can be readily followed by referring to theaccompanying drawings, without further description.

Although I have herein shown and described only a few forms of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims Without departing from the spirit and scope of my invention.

Having thus described my invention, What I claim is:

1. In a three-block four-indication signal control system in which eachsignal includes a lamp and is controlled by a train approaching it inthe direction for which the signal governs traffic movements to displayan aspect comprising a steady green light or a flashing yellow light ora steady yellow light or a steady red light according as the first threeblocks in advance of the signal are unoccupied or the first two blocksin advance are unoccupied while the third block is occupied or the firstblock in advance is unoccupied while the second block is occupied or thefirst block in advance of the signal is occupied respectively, thecombination comprising, a flashing yellow control relay for each signal,means responsive to a train occupying the, third block in advance ofeach signal while the first two blocks in advance are unoccupied forenergizing the corresponding flashing yellow control relay, a flasherrelay for each signal which if energized closes and opens its front andback contacts alternately at a frequency which may be on the order offorty times per minute, means including a front contact of the flashingyellow control relay for each signal for effecting energization of theflasher relay for the same signal, a slow release lightout relay foreach signal having a first winding with a high resistance which may beof the order of 1000 ohms and having a second winding with a lowresistance which may be of the order of 0.58 ohms, an approach controlrelay for each signal normally energized but becoming deenergized inresponse to a train occupying the first block in the rear or the firstblock in advance of the corresponding signal, means controlled by afront contact of the approach control relay for each signal forenergizing the first winding of the lightout relay for the same signalin series with the lamp for the same signal, means controlled by backcontacts of the approach control relay and the flashing yellow controlrelay for each signal in series with each other and with area-r94 thesecond winding of the lightout relay for the same signal for lightingthe lamp for the same signal, and stick circuits for the first ardsecond windings of each of said lightout relays controlled by meansincluding front and back contacts respectively of the flasher relay forthe same signal and the stick circuit for said second winding includingthe lamp for the same signal for maintaining said lightout relaysenergized when said same signal is displaying its flashing yellowaspect.

2. In a three-block four-indication signal control system in which eachsignal includes a lamp and is controlled by a train approaching it inthe direction for which the signal governs traflic movements to displayan aspect comprising a steady green light or a flashing yellow light ora steady yellow light or a steady red light according as the first threeblocks in advance of the signal are unoccupied or the first two blocksin advance are unoccupied while the third block is occupied or the firstblock in advance is unoccupied while the second block is occupied or thefirst block in advance of the signal is occupied respectively, thecombination comprising, a flashing yellow control relay for each signal,means responsive to a train occupying the third block in advance of eachsignal while the first two blocks in advance are unoccupied forenergizing the corresponding flashing yellow control relay, a flasherrelay for each signal which if energized closes and opens its front andback contacts alternately at a frequency which may be on the order offorty times per minute, means including a front contact of the flashingyellow control relay for each signal for effecting energization of theflasher relay for the same signal, a slow release lightout relay foreach signal having a first winding with a high resistance which may beof the order of 1000 ohms and having a second winding with a lowresistance which may be of the order of 0.58 ohm, an approach controlrelay for each signal normally energized but becoming deenergized inresponse to a train occupying the first block in the rear or the firstblock in advance of the corresponding signal, control means includingfront and back contacts of the approach control relay for each signalfor effecting energization of said first and second windingsrespectively of the lightout relay for the same signal in series withthe lamp of the same signal, and stick circuits for said first andsecond windings of each of said lightout relays controlled by meansincluding front and back contacts respectively of the flasher relay forthe same signal and the stick circuit for said second winding includingthe lamp for the same signal for maintaining said lightout relaysenergized when said same signal is displaying its flashing yellowaspect.

3. In a three-block four-indication signal control system in which eachsignal includes a lamp and is controlled by a train approaching it inthe direction for which the signal governs traflic movements to displayan aspect comprising a steady green light or a flashing yellow light ora steady yellow light or a steady red light according as the first threeblocks in advance of the signal are unoccupied or the first two blocksin advance are unoccupied while the third block is occupied or the firstblock in advance is unoccupied while the second block is occupied or thefirst block in advance of the signal is occupied respectively, thecombination comprising, a flashing yellow control relay for each signal,means responsive to a train occupying the third block in advance of eachsignal while the first two blocks in advance are unoccupied forenergizing the correspond ing flashing yellow control relay, a flasherrelay for each signal which if energized closes and opens its front andback contacts alternately at a frequency which may be on the order offorty times per minute, means including a front contact of the flashingyellow control relay for each signal for effecting energization of theflasher relay for the same signal, a slow release lightout relay foreach signal having a first winding with a high resistance which may beof the order of 1000 ohms and having a second winding with a lowresistance which may be of the order of 0.58 ohm, an approach controlrelay for each signal normally energized but becoming deenergized inresponse to a train occupying the first block in the rear or the firstblock in advance of the corre sponding signal, pickup circuit means forsaid first and second windings of the lightout rel y for each signalincluding front and back contacts respectively of the approach controlrelay for the same signal in series with the lamp for the same signal,and stick circuit means for said first and second windings of each ofsaid lightout relays including front and back contacts respectively ofthe flasher relay for the same signal and the stick circuit means forsaid second winding including also the lamp for the same signal formaintaining said lightout relays energized when said same signal isdisplaying its flashing yellow aspect.

4. In a three-block four-indication signal control system in which eachsignal includes a lamp and is controlled by a train approaching it inthe direction for which the signal governs traflic movements to displayan aspect comprising a steady green light or a flashing yellow light ora steady yellow light or a steady red light according as the first threeblocks in advance of the signal are unoccupied or the first two blocksin advance are unoccupied while the third block is occupied or the firstblock in advance is unoccupied while the second'block is occupied or thefirst block in advance of the signal is occupied respectively, thecombination comprising, a flashing yellow control relay for each signal,means responsive to a train occupying the third block in advance of eachsignal while the first two blocks in advance are unoccupied forenergizing the corresponding flashing yellow control relay, a flasherrelay for each signal which if energized closes and opens its front andback contacts alternately at a frequency which may be on the order offorty times per minute, means including a front contact of the flashingyellow control relay for each signal for efiecting energization of theflasher relay for the same signal, a slow release lightout relay foreach signal having a first winding with a high resistance which may beof the order of 1000 ohms and having a second winding with a lowresistance which may be of the order of 058 ohm, an approach controlrelay for each signal normally energized but becoming deenergized inresponse to a train occupying the first block in the rear or the firstblock in advance of the corresponding signal, pickup circuit means forsaid first and second windings of the lightout relay for each signalincluding front and back contacts respectively of the approach controlrelay for the same signal in series with the lamp for the same signal,and said pickup circuit means for said second winding also including aback contact of said flashing yellow control relay for the same signal,an energy storing device for each signal, means including a frontcontact of the lightout relay for each signal in series with a backcontact of the flasher relay for the same signal for charging the energystoring device for the same signal, a stick circuit for the secondwinding of the lightout relay for each signal controlled by meansincluding back contacts of the flasher and approach control relays forthe same signal in series with the lamp for the same signal, and a stickcircuit for the first winding of the lightout relay for each signalincluding front contacts of the flasher and lightout relays for the samesignal in series with the energy storing device for the same signal formaintaining said lightout relays energized when said same signal isdisplaying its flashing yellow aspect.

5. In a three-block four-indication signal control systern in which eachsignal includes a lamp and is controlled by a train approaching it inthe direction for which the signal governs traflic movements to displayan aspect comprising a steady green light or a flashing yellow light ora steady yellow light or a steady red light according as the first threeblocks in advance of the signal are unoccupied or the first two blocksin advance are unoccupied while the third block is occupied or the firstblock in advance is unoccupied while the second block is occupied or thefirst block in advance of the signal is occupied respectively, thecombination comprising, a flasher relay for each signal which ifenergized closes and opens its contacts repeatedly at a given frequency,means responsive to a train occupying the third block in advance of eachsignal while the first two blocks in advance are unoccupied forenergizing the flasher relay for the same signal, a slow releaselightout control relay for each signal having a first winding with ahigh resistance and a second winding with a low resistance, an approachcontrol relay for each signal normally energized but becomingdeenergized in response to a train occupying the first block in the rearor the first block in advance of the corresponding signal, pickupcircuit means for the first and second windings of the lightout relayfor each signal controlled by means including front and back contactsrespectively of the approach control relay for the same signal in serieswith the lamp for the same signal, stick circuit means for said firstand second windings of each of said lightout relays controlled by meansincluding front and back contacts respectively of the flasher relay forthe same signal and the stick circuit means for said second windingincluding the lamp for the same signal for maintaining said lightoutrelays energized when said same signal is displaying its flashing yellowaspect, and a front contact of the lightout relay for each signalincluded in control means for the next signal in the rear.

6. In a control arrangement for a three-block fourindication signalingsystem in which a signal for each block is of the type comprising amechanism and a lamp, in which the mechanism for each signal iscontrolled by traffic responsive means to occupy a first position ifthere is no train on any of the first three blocks in advance of thecorresponding signal and to occupy a second position if there is a trainon the second or the third block in advance of the corresponding signalwhile there is no train on the first block in advance of thecorresponding signal, the combination comprising for each signal, aflasher relay which if energized closes and opens its front and backcontacts, alternatively a given number of times per minute, meansresponsive to a train on the third block. in advance of the signal whilethere is no train on the first or the second block in advance of thesignal for energizing the flasher relay for the signal, a slow releaselightout relay having a first Winding with a high resistance and asecond winding with a low resistance, an approach control relay normallyenergized but becoming deenergized in response to a train on the firstblock in the rear or on the first block in advance of the signal, pickupcircuit means for said first and second windings of said lightout relaycontrolled by means including front and back contacts respectively ofsaid approach control relay in series with the lamp for thecorresponding signal and the pickup circuit means for said secondwinding also including a contact which is closed by traflic responsivemeans at all times except when there is a train on the third block inadvance of the corresponding signal while there is no train on eitherthe first or the second block in advance of the corresponding signal,stick circuit means for said first and second windings of said lightoutrelay controlled by means including front and back contacts respectivelyof said flasher relay for maintaining said lightout relay energized whensaid first block to the rear of said signal and said third block inadvance of said signal are occupied, said stick circuit means for saidsecond winding also including the lamp for said corresponding signal,and a front contact of said lightout relay included in control means forthe mechanism of the corresponding signal.

7. in a control arrangement for a three-block fourindication signalingsystem in which a signal for each block is of the type comprising amechanism and a lamp, in which the mechanism for each signal iscontrolled by traflic responsive means to occupy a first position ifthere is no train on any of the first three blocks in advance of thecorresponding signal and to occupy a second position if there is a trainon the second or the third block in advance of the corresponding signalwhile there is no train on the first block in advance of thecorresponding signal, the combination comprising for each signal, aflasher relay which if energized closes and opens its front and backcontacts alternately a given number of times per minute, meansresponsive to a train on the third block in advance of the signal whilethere is no train on the first or the second block in advance of thesignal for energizing the flasher relay for the signal, a slow releaselightout relay having a first winding with a high resistance and asecond winding with a low resistance, an approach control relay normallyenergized but becoming deenergized in response to a train on the firstblock in the rear or on the first block in advance of the signal, pickupcircuit means for said first winding of said lightout relay controlledby means including a front contact of said approach control relay inseries with the lamp for the corresponding signal, stick circuit meansfor said first and second windings of said lightout relay controlled bymeans including front and back contacts respectively of said flasherrelay for maintaining said lightout relay energized when said firstblock to the rear of said signal and said third block in advance of saidsignal are both occupied, said stick circuit means for said secondwinding also including the lamp for said corresponding signal, and afront contact of said lightout relay included in control means fortraflic governing means.

8. In combination, a stretch of railway track divided into a first and asecond and also a third block arranged in the order named, a signal forgoverning trafiic movements in a given direction over said blocks insaid order, said signal comprising a mechanism and a lamp, trafficresponsive means for eifecting operation of said signal mechanism to afirst position if said three blocks are unoccupied and to a secondposition if said second or said third block is occupied while said firstblock is unoc cupied, a flasher relay which if energized closes andopens its front and back contacts alternately a given number of timesper minute, means responsive to a train on said third block while thereis no train on said first or said second block for energizing saidflasher relay, an approach control relay normally energized but becomingdeenergized in response to a train approaching said signal in said givendirection within a given distance in the rear of said signal, a slowrelease lightout relay having a first winding with a high resistance anda second winding with a low resistance, a pickup circuit for said firstwinding controlled by a front contact of said approach control relay andincluding said lamp of said signal, stick circuits for said first andsecond windings including front and back contacts respectively of saidflasher relay and said stick circuit for said second winding alsoincluding said signal lamp for maintaining said lightout relay energizedwhen said first block to the rear of said signal and said third block inadvance of said signal are both occupied, and a front contact of saidlightout relay included in control means for trafiic governing means.

9. In combination, a railway signal comprising a mechanism and a lampfor governing traffic movements in a given direction over a first and asecond and also a third railway track block in the order named, trafiicresponsive means for effecting operation of said signal mechanism to afirst position if all three of said blocks are unoccupied and to asecond position if said second or said third block is occupied whilesaid first block is unoccupied, a flasher relay which if energizedrepeatedly closes and opens its front and back contacts alternately at agiven frequency, means controlled by said traflic responsive means foreflecting energization of said flasher relay only if said third block isoccupied while said first and second blocks are unoccupied, a slowrelease lightout relay having a first winding with high resistance and asecond winding with low resistance, an approach control relay normallyenergized but becoming deenergized in response to a train approaching insaid given direction Within a given distance in the rear of said signal,a pickup circuit for said first winding including a front contact ofsaid approach control relay in series wtih said signal lamp, a stickcircuit for said second winding including back contacts of said flasherand approach control relays in series with said signal lamp formaintaining said lightout relay energized when a train traveling in saidgiven direction is Within said given distance to the rear of said signaland said third block in advance of said signal is also occupied, anenergy storing device, a circuit controlled by a back contact of saidflasher relay for charging said energy storing device, a stick circuitfor said first winding including said energy storing device and a frontcontact of said flasher relay for maintaining said lightout relayenergized when a train traveling in said given direction is within saidgiven distance to the rear of said signal and said third block inadvance of said signal is also occupied, and a front contact of saidlightout relay included in control means for traflic governmg means.

10. In a control system for a signal for governing traflic movements ina given direction over a given stretch of railway track, said signalcomprising a mechanism and a lamp, in which control means is providedfor at times effecting operation of said mechanism to a given firstposition and for at other times effecting operation of said mechanism toa second position, the combination comprising, a flasher relay whichwhile energized closes its front and back contacts alternately at agiven frequency, means controlled by said control means for energizingsaid flasher relay when said control means is in condition for effectingoperation of said mechanism to said second position, a slow releaselightout relay having a first winding with high resistance and a secondwinding with low resistance, an approach control relay normallyenergized but becoming deenergized in response to a train approachingsaid signal within a given distance on said track in said givendirection, a pickup circuit for said first winding controlled by a frontcontact of said approach control relay and including said signal lamp,:1 stick circuit for said second winding controlled by back contacts ofsaid flasher and approach control relays and including said signal lampfor maintaining said lightout relay energized when said flasher relay isenergized and said approach control relay is deenergized, a stickcircuit for said first Winding controlled by a front contact of saidflasher relay, and a front contact of said lightout relay included incontrol means for traffic governing means.

References Cited in the file of this patent UNITED STATES PATENTS2,150,579 Crago Mar. 14, 1939 2,241,958 Pflasterer May 13, 19412,526,429 Staples Oct. 17, 1950 2,638,536 Tizzard May 12, 1953

